“Using high-resolution satellite imagery, researchers counted the population of polar bears (Ursus maritimus) on Rowley Island in Foxe Basin in the Canadian Arctic. … [They] were able to discriminate among presumed bears and non-targets by comparing high resolution images collected at different points in time.” (http://news.mongabay.com/2014/0717-hance-polar-bears-satellite.html)

This ‘if it moves it’s a polar bear’ criterion critically differs from the land-based count where ‘if it moves you’re too late.’